Thermophysical and thermochemical properties of new thermal … · 2017. 11. 7. · Thermophysical and thermochemical properties of new thermal barrier materials based on Dy 2 O 3-Y

Thermophysical and thermochemical properties of new thermal barrier materials based on Dy2O3-

Y2O3 co-doped zirconia

1

Thermophysical and thermochemical properties of new thermal barrier

materials based on Dy2O3-Y2O3 co-doped zirconia

Liu Qu1 and Kwang-Leong Choy1*

1UCL Institute for Materials Discovery, University College London, 20 Gordon Street, London

WC1H 0AJ, United Kingdom

*Corresponding author. Tel/fax: +44 2076793855

E-mail address: [email protected] (Kwang-Leong Choy)

Abstract

Dy2O3-Y2O3 co-doped ZrO2 would potentially give lower thermal conductivity and higher coefficient

of thermal expansion, which is a promising ceramic thermal barrier coating material for aero gas

turbines and high temperature applications in metallurgical and chemical industry. In this study,

Dy2O3-Y2O3 co-doped ZrO2 ceramics were prepared using solid state reaction methods. Dy0.5Zr0.5O1.75

and Dy0.25Y0.25Zr0.5O1.75 consist of pure cubic fluorite phase, whereas both Dy0.06Y0.072Zr0.868O1.934 and

Dy0.02Y0.075Zr0.905O1.953 have tetragonal and cubic composite phases. The influence of the chemical

composition on coefficient of thermal expansion (CTE) and the thermal conductivity was investigated

by varying the content of rare earth dopant. Dy0.06Y0.072Zr0.868O1.934 exhibited a lower thermal

conductivity and higher coefficient of thermal expansion as compared with standard 8 wt.% Y2O3

stabilized ZrO2 which is used in conventional thermal barrier coatings. The compatibility between the

thermally grown oxide that consists of Al2O3 and the new compositions is critical to ensure the

durability of thermal barrier coatings. Hence, the compatibility between Al2O3 and Dy2O3-Y2O3 co-

doped YSZ was investigated by mixing two types of powders and eventually sintered at 1300˚C.

Dy0.06Y0.072Zr0.868O1.934 is compatible with Al2O3, whereas YAlO3 and Dy3Al2(AlO4)3 were formed

when Dy0.25Y0.25Zr0.5O1.75 and Al2O3 were mixed and sintered.

Keywords: New thermal barrier materials; rare earth doped ceramics; thermal conductivity;

thermal expansion coefficient; thermochemical compatibility

1. Introduction

ZrO2 partially stabilized with 6-8 wt% Y2O3 (i.e. 3-4.5 mol% Y2O3 partially stabilized ZrO2) is

commonly used as a thermal barrier coating material for gas turbine components to protect them from

high operating temperatures and hot corrosion. Thermal barrier coatings (TBCs) are a complex system

and the durability and engine efficiency are critical factors to be considered in the development of

new TBCs [1]. The t’-tetragonal 6-8 wt% YSZ would transform into tetragonal and cubic phases, and

further into monoclinic phase, bringing about thermal mismatch between the bond coat and the top

coat at around 1200˚C [2]. Furthermore, the formation of cracks within TBCs can reduce the life time

mailto:[email protected]



2

of the TBCs and increase the cost for the whole process in industry [3]. Rare earth oxide doped ZrO2

has been considered as a substitute for the conventional 6-8 wt% YSZ because of the potential

improved material properties such as reduced thermal conductivity and enhanced phase stability at

much higher temperatures. Various types of new TBC materials have been developed, such as ABO3

perovskite structure [4], A2Zr2O7 pyrochlore structure [5] and A2Zr2O7 defect fluorite structure [6].

Although rare earth oxides such as La2O3 and Sm2O3 have been used as dopants to reduce the thermal

conductivity and enhance the operating temperature of the engine, limited studies have been

conducted on Dy2O3 as a dopant [5, 7]. Dy2O3 doped ZrO2 gives a stable fluorite phase between room

temperature and high temperature (2900°C) in a relatively wide composition [8]. 5-20% Dy2O3 doped

5YSZ have been investigated by Wang, summarizing that the 10% Dy and Y co-doped ZrO2 coatings

gave a higher resistance to heat transfer. Air plasma spraying method was used in Wang’s work and

the obtained thermal conductivity was around 0.6-0.75 W/mK. Thermal barrier coating deposited by

plasma spray method exhibits a typical thermal conductivity of 0.8-1.7 W/mK, and using Electron

Beam Physical Vapor Deposition (EBPVD) it has a thermal conductivity of 1.5-2 W/mK [1].

A variety of methods can be used to fabricate the high temperature ceramic coatings including the

commercial EBPVD and Plasma Spray (PS) methods, Chemical Vapor Deposition (CVD) method [9],

Electrostatic Spray-Assisted Vapour Deposition (ESAVD) method [10], etc. Solid state method and

chemical/liquid route have also been widely used to produce 6-8 wt% YSZ bulk samples for

mechanical, chemical and physical properties investigation. This paper highlights the development of

new thermal barrier materials based on Dy2O3-Y2O3 co-doped ZrO2 and investigates their

thermophysical properties as well as their thermochemical stability. In order to conduct this study,

Dy2O3-Y2O3 co-doped ZrO2 was fabricated using a solid state reaction method. The thermochemical

compatibility between the thermally grown oxide layer which consisting of Al2O3 and new thermal

barrier materials was investigated. In addition, thermophysical and thermochemical properties such as

thermal conductivity and CTE were also being characterized. The effects of co-dopants Dy2O3-Y2O3

on these properties were established.

2. Experimental

ZrO2 powders (Sigma-Aldrich), Y2O3 powders (Alfa Aesar, 99.99%), Dy2O3 powders (Advanced

Materials Resources) and ZrO2 partially stabilized with 4 mol% Y2O3 [4YSZ, Zr0.923Y0.077O1.962,

(Tosoh Corporation)] were used as the starting materials. The Dy0.5Zr0.5O1.75 [DZ], Dy0.25Y0.25Zr0.5O1.75

[DYZ], Dy0.06Y0.072Zr0.868O1.934, Dy0.02Y0.075Zr0.905O1.953 and 4YSZ powders were synthesized via solid

state reaction. Dy0.5Zr0.5O1.75 was prepared by mixing Dy2O3 and ZrO2 powders with a molar ratio of

1:2 in distilled water and 3 wt.% organic binder and 3 wt.% organic dispersant. The solution was

subsequently stirred for 30 min. Similarly, Dy0.25Y0.25Zr0.5O1.75 was prepared by mixing Dy2O3, Y2O3

and ZrO2 powders with a molar ratio of 1:1:4 in distilled water as well as 3 wt.% organic binder and 3

wt.% organic dispersant. For Dy0.02Y0.075Zr0.905O1.953 and Dy0.06Y0.072Zr0.868O1.934 powders, Dy2O3 and



3

YSZ were mixed with 3 wt.% organic binder and 3 wt.% organic dispersant in distilled water,

followed by 30 min stirring process. The molar ratio of DyO1.5 was 2% and 6%, respectively. The

standard 4YSZ powders were mixed with 3 wt.% organic binder and 3 wt.% organic dispersant in

distilled water. After drying, the dried powders were ball milled for 8h and compacted into pellets,

followed by pressureless sintering at 1400˚C with a heating rate of 7°C/min in the air atmosphere. The

typical sintering time was 6h, while the sintering time for DYZ and DZ was increased to 12h and 18h

to investigate the thermal behaviour of the as-synthesized pellets.

The crystal structure of Dy2O3-Y2O3 co-doped ZrO2 was characterized using X-ray diffractomer

(Siemens D500, Cu Kα radiation) and Raman spectroscopy (Olympus BX41, He-Ne laser source

632.8 nm). The scanning step is 0.05° and the time step is 2s. The tension of the generator is The

surface morphology of the particle and pellets were examined by the scanning electron microscope

(SEM, Phillips XL30 ESEM-FEG). Coefficient of thermal expansion was measured from 100˚C to

1000˚C at a heating rate of 5˚C/min using a Thermalmechanical Analyzer (TMA, TA Instruments,

Q400). The thermal conductivity of the pellets was measured using a TCi thermal conductivity

analyser (C-Therm) at room with a thermal paste (Wakefield 120). The relative density was

determined by measuring the density of the pellet and calculating the theoretical density of each

chemical composition. The bulk density was determined via measuring the weight and the volume of

the pellet directly. The bulk thermal conductivity can be calculated based on the porosity and the

measured thermal conductivity using equation (1),

𝜅𝑑𝑒𝑛𝑠𝑒 = 𝜅𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑1

1−1.5𝜑, (1)

where φ is the porosity, κmeasured is the measured thermal conductivity and κdense is the thermal

conductivity for the dense material (Schlichting, Padture et al. 2001). The calculation of dense thermal

conductivity is based on certain approximations including the spherical pores incorporated into the

homogeneous medium, the thermal conductivity for pores is infinite, overall thermal conductivity k of

porous materials is a sum of phonon scattering kP and photon scattering kR.

3. Results and Discussion

(a) SEM

The SEM images of co-doped Dy0.25Y0.25Zr0.5O1.75 [DYZ] and Dy0.5Zr0.5O1.75 [DZ] are shown in Figure

1 (a) and (b), respectively. The recrystallization region (i.e. circled area) in which open pores were

closed due to the diffusion of ions, was higher within DZ pellets than that in DYZ pellets. Open pores

were on the surface of both the pellets and the shape of these pores was more homogeneous on DYZ

pellets than that on DZ pellets. Furthermore, from the surface morphology point of view, the DYZ

pellet had more pores as compared with the DZ pellet. The open pore area on the surface of the DYZ

pellet was 24.7%± 0.7% while it was 33.7%±0.1% for the DZ pellet.



4

(a) DYZ pellet (b) DZ pellet

Figure 1 SEM images for: (a) DYZ pellet; (b) DZ pellet

(b) XRD

The sintered 4YSZ, Dy0.02Y0.075Zr0.905O1.953 and Dy0.06Y0.072Zr0.868O1.934 consisted of cubic and

tetragonal phases. Dy0.25Y0.25Zr0.5O1.75 and Dy0.5Zr0.5O1.75 pellets exhibited pure cubic fluorite phase.

Figure 2 XRD patterns for Dy0.25Y0.25Zr0.5O1.75, Dy0.5Zr0.5O1.75, Dy0.02Y0.075Zr0.905O1.953 and Dy0.06Y0.072Zr0.868O1.934



5

The crystal size can be estimated based on line broadening using Scherrer equation (2),

𝐷𝑋𝑅𝐷 = 𝜆𝐾

𝐵∙𝑐𝑜𝑠Ɵ, (2)

where D is the dimension of crystalline, λ is the wavelength (Cu Kα), Ɵ is the diffraction angle, k is

the constant (~0.9) and B is the full-width half maximum (FWHM) [11]. The FWHM can be

determined based on equation (3),

𝐵𝑝2(2Ɵ) = 𝐵ℎ

2(2Ɵ) − 𝐵𝑓2(2Ɵ), (3)

where Bp(2Ɵ) is the true half maximum width, Bh(2Ɵ) is the measured half maximum width of the

sample and Bf(2Ɵ) the standard half maximum width [12]. The 𝜆𝐶𝑢𝐾𝛼 = 1.5406 × 10−10𝑚, and the

standard material is LaB6 300.

Figure 3 The crystal dimension of Dy0.5Zr0.5O1.75 and Dy0.25Y0.25Zr0.5O1.75 (1 1 1)

With the increase in sintering time, the crystal dimension of (1 1 1) for DZ pellets increased linearly

and the crystal size for (1 1 1) DYZ pellets also increased. The grain growth due to sintering

contributes to the decrease of grain boundaries, hence reducing the phonon scattering sources. As a

result, the thermal conductivity of the pellets would increase with increasing sintering time. Moreover,

the crystal size increment for DYZ pellets between 12 hrs and 18 hrs was 5.75% and for DZ was

20.32%. During the long sintering time, the DYZ pellet exhibited a much lower increase in percentage

as compared with DZ pellet. The reason for the difference of the grain growth between 12h and 18h

for the two compositions can probably due to the different types of rare earth dopants and

concentration in DYZ and DZ which exhibiting different migration processes at high temperature.

Because the grain boundary growth is achieved via the diffusion of oxygen vacancies at the grain

boundary, Dy3+ and Y3+ cations can diffuse at the grain boundary during the high-temperature

calcination [13, 14]. Moreover, the migration enthalpies for Dy3+ is higher that Y3+ in ZrO2 system at



6

1273K, indicating that during the initial period, in DYZ Y3+ cations diffuse while in DZ Dy3+ cations

diffuse [15]. The crystal size for the Dy0.02Y0.075Zr0.905O1.953, Dy0.06Y0.072Zr0.868O1.934 and 4YSZ was not

calculated due to the fact that the phases were tetragonal and cubic phases which cannot be

determined using Scherrer equation.

(c) Raman analysis

The Raman spectrum for each composition is shown in Figure 4. Defect fluorites such as

Dy0.5Zr0.5O1.75 and Dy0.25Y0.25Zr0.5O1.75 would give a single broad band Raman active mode. In Raman

spectra, the broadband and low intensities are attributed to the defect fluorite in which the two cation

sites are disordered and 1/8 of the anions are absent [16]. Such randomly distributed oxygen ions can

bring about broad and continuum density of states [17]. Raman broadening can also be a result of

structure disorder and the strain within a crystal [18]. Besides, there are six active Raman modes for t-

YSZ from 100 to 800 cm-1 and five active modes have been detected within 200 to 1000 cm-1 due to

the Raman shift range limitation (Viazzi et al., 2008). 263 cm-1 is Eg stretching mode; 321 cm-1

indicates Zr-O B1g bending mode; 467 cm-1 is Zr-O stretching Eg mode; 614 cm-1 is the symmetric O-

Zr-O A1g stretching mode; 641 cm-1 is the asymmetric O-Zr-O Eg stretching mode [19].

(a) (b)

Figure 4 Raman spectrum for: (a) DZ and DYZ with 12h calcination; (b) Dy0.02Y0.075Zr0.905O1.953 and

Dy0.06Y0.072Zr0.868O1.934 with 6h calcination

(d) Thermal conductivity

The thermal conductivities of the sintered pellets are shown in Figure 5. DYZ exhibited lower values

for thermal conductivity than 4YSZ which is used in the conventional thermal barrier coatings. In

addition, when the sintering time increased from 6h to 12h, the thermal conductivity for DZ increased

from 1.60 W/mK to 2.40 W/mK, while for DYZ it increased from 1.14 W/mK to 2.41 W/mK.



7

Figure 5 Thermal conductivity of various ceramic thermal barrier materials

The reasons could be that the addition of Dy2O3 can create more oxygen vacancies than YSZ [7]. In

the solid solution, Zr4+ cation was substituted by Dy3+ and Y3+ cations with the incorporation of

oxygen vacancies for charge compensation. For instance, based on the defect chemistry and Kroger-

Vink notation,

𝐷𝑦2𝑂3 𝑍𝑟𝑂2→ 2𝐷𝑦𝑍𝑟

, + 𝑉𝑂,, + 3𝑂𝑂

𝑥 (4)

where 𝐷𝑦𝑍𝑟,

indicates Dy3+ cation taking the Zr4+ cation site with single negative charge, 𝑉𝑂,, is an +2

oxygen vacancy with double positive charges, and 𝑂𝑂𝑥 represents O2- anion on the oxygen site with

neutral charge [7]. The mean free path of phonons which can be significantly scattered by point

defects such as lattice strain, cracks and porosity, is calculated using equation (5),

1

𝑙𝑝=

𝑎3

4𝜋𝜈𝑚4 𝜔

4𝑐 (∆𝑀

𝑀)2 (5)

where a3 is the volume per atom, c is the defect concentration per atom, vm is the transverse wave

speed, ω is the phonon frequency, M is the average mass of the host atom and ΔM the mass

differences between the substituted and the substituting atoms [20]. The atomic weight of Dy (162.5)

is much heavier than that of Y (88.906) resulting in the higher scattering of phonon and photon in

DYZ as compared with that in DZ due to the fact that the mean free path of the phonon is in

proportion with the square of the atomic mass difference [21]. Furthermore, with increasing rare earth

content, the thermal conductivity decreased and then remained relatively stable probably due to the

different crystal structure and defect distribution. In defect fluorites DYZ and DZ, the phase consisted

of pure cubic phase, whereas in Dy0.06Y0.072Zr0.868O1.934, both tetragonal and cubic existed. Although

mass differences and defects such as oxygen vacancies in DYZ and DZ were higher than those in



8

Dy0.06Y0.072Zr0.868O1.934 because of the higher molar percentages, the overall thermal conductivities

were comparable among fluorite DYZ and DZ, tetragonal and cubic Dy0.06Y0.072Zr0.868O1.934.

(e) Coefficient of thermal expansion

The coefficient of thermal expansion (CTE) for each composition was measured from room

temperatures to 1000˚C. The Dy2O3-Y2O3 co-doped ZrO2 exhibited enhanced CTE with the increase

in the concentration of the dopant as compared with 4YSZ.

Figure 6 CTE for various ceramic thermal barrier materials from 100 to 1000˚C (units of CTE refer to 10-6/°C)

In the high temperature range, with the increase in the concentration of the rare earth oxide dopant

from 2% to 6%, the CTE values increased continuously. The increased content in the dopants resulted

in the increase of the concentration of oxygen vacancies and other defects in the YSZ lattice because

of the valence difference between rare earth ions and zirconium ions [22]. Furthermore, it has been

reported that for A2Zr2O7 pyrochlore and fluorite structure, Zr-O bond is the most critical parameter

influencing CTE after which A-O is the second most important factor while an O-O bond has little

influence on the CTE and fluorite structure, which has a weaker Zr-O bond and gives higher CTE

than pyrochlore [23]. The presence of defects such as voids, debonding, grain boundary and cracks

may weaken the atomic bond and thus can enhance the CTE values. Moreover, the CTE of rare earth

doped ZrO2 increases with decreasing dopant radius [24], Dy3+ is one of the smallest rare earth ions

and DYZ has the potential to exhibit a much lower CTE than 4YSZ. However, DZ exhibited higher

CTE values than YSZ when temperature is high than 800°C, while YSZ had higher CTE values than

DYZ over 100-1000°C. The reason can be due to the fact that DYZ and DZ exhibited cubic phase

while 4YSZ had tetragonal and cubic phases which involving defects such as phase boundaries. These

defects can further weaken the atomic bond and increase CTE.



9

(f) Thermochemical compatibility

The phase composition of the sintered mixture of Al2O3 and Dy2O3-Y2O3 co-doped ZrO2 is shown in

the XRD pattern. In the DYZ and Al2O3 mixture, there are new phases, YAlO3 and Dy3Al2(AlO4)3,

while in the Al2O3 and Dy0.06Y0.072Zr0.868O1.934 mixture, no any new phase has been detected.

(a)

(b)

Figure 7 XRD pattern of the mixed powders of: (a) Al2O3 and (DyY)0.25Zr0.5O1.75; (b) Al2O3 and

Dy0.06Y0.072Zr0.868O1.934

The compatibility between Al2O3 and Dy2O3-Y2O3 co-doped ZrO2 can be studied via sintering the

mixture of a 50 wt.% of each type of powders. After 1400˚C 8h sintering, the DYZ powders reacted

with Al2O3, YAlO3 and Dy3Al2(AlO4)3 were formed while no new phases were detected in the mixture

of Al2O3 and Dy0.06Y0.072Zr0.868O1.934 powders. This can be a result of higher driving forces of the inter-

diffusion of Dy ions into Al2O3 crystals when the content of rare earth oxides increased. From 1600°C

onwards, Dy2O3 reacted with Al2O3 forming new solid state solutions with varied chemical

compositions (Figure 8) [25]. In the solid state reaction, the reaction between Al2O3 and Dy2O3-Y2O3

co-doped ZrO2 depends on the diffusion of Al3+, Dy3+ and Y3+, which is controlled by a parabolic rate

law [26],

𝑑𝑥

𝑑𝑡= 𝑘 ∙ 𝑥−1, (6)



10

where x is the amount of reaction, t is time and k is rate constant. With the increase of the thickness of

the reaction layer between Al2O3 and Dy2O3-Y2O3 co-doped ZrO2, the reaction rates decreased. Other

factors that influence the reaction rates include the surface area and the contact area between the solid

oxide, the rate of nucleation of the new phase, and the diffusion rate of ions. Therefore, the reaction

between Al2O3 and DYZ could occur readily, whereas Dy0.06Y0.072Zr0.868O1.934 is thermochemically

stable with Al2O3. The solid state reaction is a slow process even at high temperatures because it

involves the breaking of chemical bonds and the migration of ions, which requires sufficient thermal

energy to allow the ions to diffuse through the lattice.

Figure 8 Binary phase diagram of Dy2O3-Al2O3 [25]

Such new perovskite phase which has lower CTE as compared with t-YSZ can bring about thermal

stress at the interfaces of TBCs at high temperatures and hence influence the performance of the new

TBCs [27]. The compatibility between Al2O3 and Dy2O3-Y2O3 co-doped ZrO2 can be maintained

when the content of oxide dopants (DyO1.5 and YO1.5) reached up to 13 mol% using solid state

processes. Moreover, in a thermal barrier coating, the composition of the mixed zone of the thermally

grown oxide and the ceramic top coat can delaminate when the interfaces are not compatible [28]. The

new composition of Dy2O3-Y2O2 co-doped ZrO2 exhibited promising properties as ceramic thermal

barrier materials for gas turbines in aero engines.

4 Conclusions

In conclusion, Dy0.25Y0.25Zr0.5O1.75 and Dy0.5Zr0.5O1.75 produced pure cubic fluorite phase, while

Dy0.06Y0.072Zr0.868O1.934 and Dy0.02Y0.075Zr0.905O1.953 consisted of tetragonal and cubic phases. Dy2O3-



11

Y2O3 co-doped ZrO2 exhibited lower thermal conductivity and higher coefficient of thermal

expansion as compared with 4YSZ. Dy0.06Y0.072Zr0.868O1.934 produced the lowest thermal conductivity

and relatively higher CTE amongst the other chemical compositions. The presence of Dy3+ in the

zirconia lattice creates lattice strain and oxygen vacancies which are strong phonon scattering points

and weaken the chemical bonding. The thermochemical compatibility between the Al2O3 and the

Dy2O3-Y2O3 co-doped ZrO2 has been controlled by the content of the rare earth oxides.

Dy0.25Y0.25Zr0.5O1.75 can react with Al2O3 to form YAlO3 and Dy3Al2(AlO4)3; Dy0.06Y0.072Zr0.868O1.934 is

compatible with Al2O3.

Acknowledgements

One of the authors, Liu Qu would like to acknowledge the Dean of Engineering Research Scholarship

for International Excellence, the University of Nottingham

References

[1] N.P. Padture, M. Gell, E.H. Jordan, Thermal barrier coatings for gas-turbine engine applications,

Science 296 (Journal Article) (2002) 280-284.

[2] U. Schulz, K. Fritscher, M. Peters, Thermocyclic behavior of variously stabilized EB-PVD

thermal barrier coatings, Journal of Engineering for Gas Turbines and Power 119 (4) (1997) 917-

921.

[3] X. Cao, R. Vassen, W. Fischer, F. Tietz, W. Jungen, D. Stӧver, Lanthanum-cerium oxide as a

thermal-barrier-coating material for high-temperature applications, Advanced Materials 15 (17)

(2003) 1438-1442.

[4] W. Ma, D. Mack, J. Malzbender, R. Vaßen, D. Stöver, Yb2O3 and Gd2O3 doped strontium

zirconate for thermal barrier coatings, Journal of the European Ceramic Society 28 (16) (2008)

3071-3081.

[5] H. Zhang, K. Sun, Q. Xu, F. Wang, L. Liu, Thermal conductivity of (Sm1-xLax)2Zr2O7 (x=0, 0.25,

0.5, 0.75 and 1) oxides for advanced thermal barrier coatings, Journal of Rare Earths 27 (2)

(2009) 222-226.

[6] Z.G. Liu, J.H. Ouyang, Y. Zhou, J. Li, X.L. Xia, Influence of ytterbium- and samarium-oxides

codoping on structure and thermal conductivity of zirconate ceramics, Journal of the European

Ceramic Society 29 (4) (2009) 647-652.

[7] X. Qiang, P. Wei, W. Jingdong, Q. Longhao, M. Hezhuo, K. Mori, T. Torigoe, Preparation and

thermophysical properties of Dy2Zr2O7 ceramic for thermal barrier coatings, Materials Letters 59

(22) (2005) 2804-2807.

[8] C. Wang, Experimental and computational phase studies of the ZrO2-based systems for thermal

barrier coatings, in, Vol. Doctor of Philosophy, Stuttgart University, 2006.

[9] J.R.V. Garcia, T. Goto, Thermal barrier coatings produced by chemical vapor deposition, Science

and Technology of Advanced Materials 4 (Journal Article) (2003) 397-402.

[10] J.D. Vyas, K.L. Choy, Structural characterisation of thermal barrier coatings deposited using

electrostatic spray assisted vapour deposition method, Materials Science and Engineering: A 277

(1-2) (2000) 206-212.

[11] S. Farhikhteh, A. Maghsoudipour, B. Raissi, Synthesis of nanocrystalline YSZ (ZrO2–8Y2O3)

powder by polymerized complex method, Journal of Alloys and Compounds 491 (1–2) (2010)

402-405.

[12] L. Wang, Y. Wang, X.G. Sun, J.Q. He, Z.Y. Pan, C.H. Wang, A novel structure design towards

extremely low thermal conductivity for thermal barrier coatings – Experimental and

mathematical study, Materials & Design 35 (0) (2012) 505-517.



12

[13] R. Chaim, Activation energy and grain growth in nanocrystalline Y-TZP ceramics, Materials

Science and Engineering: A 486 (1–2) (2008) 439-446.

[14] U. Brossmann, R. Würschum, U. Södervall, H.-E. Schaefer, Oxygen diffusion in ultrafine

grained monoclinic ZrO2, J. Appl. Phys. 85 (11) (1999) 7646-7654.

[15] F. Yang, Electrical and thermal properties of yttria-stabilised zirconia (YSZ)-based ceramic

materials, in: Faculty of Engineering and Physical Science, Vol. Doctor of Philosophy, The

University of Manchester, 2011, pp. 173.

[16] B.P. Mandal, A.K. Tyagi, Pyrochlores: potential multifunctional materials, BARC

NEWSLETTER (313) (2010) 6-13.

[17] F.N. Sayed, V. Grover, K. Bhattacharyya, D. Jain, A. Arya, C.G.S. Pillai, A.K. Tyagi, Sm2-

xDyxZr2O7 pyrochlores: probing order-disorder dynamics and multifunctionality, Inorganic

Chemistry 50 (2011) 2354-2365.

[18] Z. Qu, C. Wan, W. Pan, Thermal expansion and defect chemistry of MgO-doped Sm2Zr2O7,

Chemistry of Materials 19 (2007) 4813-4918.

[19] S. Heiroth, R. Frison, J.L.M. Rupp, T. Lippert, E.J. Barthazy Meier, E. Müller Gubler, M. Döbeli,

K. Conder, A. Wokaun, L.J. Gauckler, Crystallization and grain growth characteristics of yttria-

stabilized zirconia thin films grown by pulsed laser deposition, Solid State Ionics 191 (1) (2011)

12-23.

[20] L. Jin, Q. Yu, L. Ni, C. Zhou, Micrustructure and thermal properties of nanostructured 8 wt.%

CeO2 doped YSZ coatings prepared by atmospheric plasma spraying, Journal of Thermal Spray

Technology 21 (5) (2012) 928-934.

[21] P.G. Klemens, Phonon scattering by oxygen vacancies in ceramics, Physica B: Condensed Matter

263–264 (0) (1999) 102-104.

[22] X. Xia, R. Oldman, R. Catlow, Computational Modeling Study of Bulk and Surface of Yttria-

Stabilized Cubic Zirconia, Chemistry of Materials 21 (15) (2009) 3576-3585.

[23] F. Qun-bo, Z. Feng, W. Fu-chi, W. Lu, Molecular dynamics calculation of thermal expansion

coefficient of a series of rare-earth zirconates, Computational Materials Science 46 (3) (2009)

716-719.

[24] M.O. Zacate, L. Minervini, D.J. Bradfield, R.W. Grimes, K.E. Sickafus, Defect cluster formation

in M2O3-doped cubic ZrO2, Solid State Ionics 128 (1-4) (2000) 243-254.

[25] R. Gilissen, A.J. Flipot, R. Lecocq, Tentative Dy2O3-Al2O3 phase diagram and preparation of

pure single-phase Dy aluminates, Journal of the American Ceramic Society 57 (8) (1974) 274.

[26] A.R. West, Solid state chemistry and its applications, John Wiley & Sons Ltd., 1985.

[27] G. Falkenberg, U. Krell, J.R. Schneider, HASYLAB Annual Report 2003, in: L. Vasylechko, A.

Matkovskii, A. Senyshyn, D. Savytskii, M. Knapp, C. Bӓhtz (Eds.) Crystal structure and thermal

expansion of orthorhombic perovskite-type RE aluminates, 2003.

[28] H. Zhao, M.R. Begley, A. Heuer, R. Sharghi-Moshtaghin, H.N.G. Wadley, Reaction,

transformation and delamination of samarium zirconate thermal barrier coatings, Surface and

Coatings Technology 205 (19) (2011) 4355-4365.

Documents

Thermophysical and thermochemical properties of new thermal … · 2017. 11. 7. · Thermophysical and thermochemical properties of new thermal barrier materials based on Dy 2 O 3-Y